The invention relates to a security device which prevents a deadbolt lock from being opened from the outer side of an associated door.
It is necessary to lock certain doors such as outside doors in a house or entry doors to an apartment or hotel room. These doors are provided with a conventional doorknob including a locking mechanism which is adapted to be operated by a key from the outer side of the door.
In order to provide greater security, a deadbolt lock is often also mounted on the door and includes a bolt having flat sides which is movable into and out of a complementary receptacle in an associated door jamb. The deadbolt lock is operated by a key from the outer side of the door, and is operated by a handle from the inner side of the door. This handle is spaced from the inner side of the door and is pivoted through a substantial angle in moving between between locked and unlocked positions. The deadbolt lock can be operated form the inner side of the door by grasping and turning the handle, while the deadbolt lock can be operated from the outer side of the door only by turning a key.
When a deadbolt lock is opened by a key, the handle also pivots through a predetermined angle. If pivoting movement of the handle from its locked position to its unlocked position is prevented, the deadbolt lock cannot be opened from the outer side of the door.
Lock picking tools have been developed which enable unauthorized persons to open deadbolt locks. Furthermore, particularly in connection with apartments, dormitories and hotel rooms, unauthorized persons may come into possession of a key to a deadbolt lock, and accordingly, the deadbolt lock does not actually provide the desired security.
Accordingly, there is a need to provide a security device which can be attached to a deadbolt lock handle at the inner side of a door which positively prevents the deadbolt lock from being opened from the outer side of the door either by a key or a lock picking tool. A number of prior art devices have been developed to accomplish this purpose as shown for example in U.S. Pat. Nos. 4,279,137, 4,715,200, 4,827,745 and 5,000,498.
These prior art devices have certain disadvantages which have limited their success and acceptance by the public. Some of the prior art devices are limited to use with handles of a certain size or configuration, while others are excessively difficult and time consuming to place in operative locking position or to release when it is desired to unlock the deadbolt lock. Difficulty in releasing the device would be particularly hazardous if a person needed to open the door quickly in the event of a fire. A further problem with these prior art devices is that they are not always readily available since they must be stored somewhere other than on the inner side of the door.